The production of X-ray images is a complex process that uses electromagnetic radiation. X-rays are high-frequency energy waves that penetrate through the body or the target organ and are either absorbed, reflected off, or traversed through the body. The X-ray tube, which produces the X-ray, is composed of a cathode and an anode. The cathode is a tungsten filament, which is heated during the process by electricity and ultimately produces electrons that travel through the tube to the target (anode). Once the high-speed electrons hit the target, producing X-rays in the form of photons.
A visible radiographic image is produced following processing of the latent or invisible image. Depending on the type of imaging system, acquiring, processing, and displaying of the image can vary significantly. However, the attributes of a quality radiographic image are similar regardless of the type of imaging system. This chapter focuses on how the image is formed and its quality after processing.
X-rays are primarily regulated by the kVp, mA setting, and exposure time. Image production can be individualized by manipulating these three factors to produce the best image. The kVp controls the energy and penetration quality of the X-ray, which is important when considering the patient's size, age, and amount of movement. The quality of the X-ray beam becomes enhanced by increasing the kVp. Contrast is also controlled by kVp by regulating the absorption of the X-ray beam. The mA setting controls the number of electrons emitted by monitoring the heating of the filament and thus controls the number of X-ray photons produced at the anode. Exposure time determines the number of X-rays. A longer exposure time increases the number of X-ray photons. Other factors that control x-ray quality or production include filtration, collimation, distance from the object or source, motion, and anatomy/pathology of the target organ or body.
Once the patient is positioned in the right spot with the anatomic target in place, X-rays pass through the body, and remnant rays strike the image receptor located behind the patient. The image receptor may be a charged electron device used in digital radiography, a photosensitive phosphor plate used in computed radiography, or a conventional film screen. In conventional radiography, X-rays pass through the body and hit a film screen receptor, a transparent film composed of a silver bromide crystal emulsion spread between polyester base sheets. Once it strikes the film, the crystals fluoresce and produce a latent image. A latent image needs further processing for it to be visible. Although it is invisible to the naked eye, it is now more sensitive to chemicals used to produce the image. After using these chemicals called developers, a process of fixation, washing, and drying takes place to create an image. In computed radiography, X-rays strike a photosensitive phosphor plate, and the resulting electrons in the phosphor particles are placed in a high-energy state, producing a latent image. The latent image is processed and scanned via lasers to develop a visible image. Digital radiography uses different chemical elements to interact with X-rays. The latent image is produced in the form of electric signals, which are directly transferred to a computer to create an image in real-time. Digital radiography is the latest advancement in image production and is currently preferable to other modalities due to its efficiency and improved quality.
Medical imaging is among the most valuable technological advancements in the field of medicine and has resulted in many improvements in the diagnosis and treatment of numerous medical conditions. Image production and evaluation have allowed healthcare professionals to efficiently recognize and assess emergent cases and have been a crucial tool in improving public health.
Examples include the use of mammography in breast cancer screening, radiography in the assessment of fractures or identifying pneumonia, ultrasound image guidance in treating tumors, and the use of multiple imaging modalities during procedures such as joint injections and in the insertion of stents, catheters, and other medical devices. Imaging aids in diagnosis and reduces the risk of unnecessary medical or surgical interventions. Medical professionals need to understand the risks and benefits of imaging and learn how to utilize imaging modalities properly. Understanding the mechanism behind image production and knowledge of the different components that affect image accuracy is crucial in optimizing image quality and providing the best care for patients.
Nursing, Allied Health, and Interprofessional Team Interventions
Understanding image production techniques and knowledge of image evaluation are crucial in proposing the appropriate diagnosis and treatment. Balancing the risks and benefits must always be done before imaging tests that utilize ionizing radiation.